Rough engine at low power

[coppercity]

A couple days ago during a training flight with a student we experienced a rough running engine while at lower power settings. We set the throttle to a position where the engine ran smoothly and returned for an uneventful landing. Looking at the indications on the EMS during the event the RIght side EGT would drop off significantly to 600-700 deg vs a 1000 on the left. My first thought was maybe a throttle cable had slipped. After opening the cowling though and inspecting the cables and throttle arms everything looked normal. Next place to look was the float bowls. I pulled the right side first since it seemed abnormal according to the EMS. Sure enough one of the floats was sunk to the bottom of the bowl! As long as the engine was at a higher power setting needing more fuel everything was fine, but as the fuel requirements went down with lower power settings and the float bowl overfilled then the engine ran rough. Replaced all the floats and everything runs like a champ again.

[Runtoeat]

Hi Eric. What was the issue with the float? Are there newer materials used for the new floats that may be more durable or less prone to absorbing fuel or leaking compared to older ones?

[Runtoeat]

Hi Roger. Thanks. Right now, it ain't broke so I ain't fixin'! Hope I don't jinx myself by saying this!

[coppercity]

In hindsight, the spark plugs on the side with the bad float had been a little darker in color at the previous 100hr, which was about 20 hrs before the failure, that may have been a sign as well. Certainly the check Roger recommends is a good method.

[Runtoeat]

Roger and Eric, as I understand your troubleshooting technique, you hold the float bowl in your hand with the float in it and add fuel to about 1/4" from the top of the bowl. If the float pin doesn't stay up with the top of the fuel, the floats (must replace both) need replacement. Correct?